In the field of computerized games and other similar types of interactive video systems, it is desirable to employ real-world images, to provide a measure of customization or personal input to a scene that is being displayed. In one example, an image of a child can be captured, and mapped to one of the characters in an interactive display, e.g. a game, so that the child appears to be a participant in the game itself. For instance, the captured image of the child could function as the "skin" in an interactive system of the type disclosed in U.S. patent application Ser. No. 08/693,028, entitled "System for Image Manipulation and Animation Using Embedded Constraint Graphics", filed Aug. 6, 1996. As an alternative to using a captured image as an a component of the personalized display, the child's image can be used as an input feature, to control elements in the display. For example, if the child waves his hand back and forth, an animated character on the screen can do the same, or perform some exaggerated version of that motion.
To perform either of these types of functions, it is necessary to identify points of reference in the captured image, or texture image, which correspond to control points on the character appearing in the video display. If a captured video stream showing a child is to appear as one of the characters in a personalized game, for example, it is necessary to identify the location of the elbow, wrist, knee, ankle, etc., so that the image can be properly manipulated to appear to move in an intended manner. Similarly, if the image of the child is to function as a control input for the play of the game, it is necessary to identify certain points on that image which correspond to the controllable points on the character to be manipulated in the video display. Identification of control points also permits an otherwise static image to be "parsed" into components that can be manipulated relative to one another to portray movement. For instance, an image of a child's favorite stuffed animal can be manipulated so that it appears to be walking around on the computer screen.
In the past, the identification of correspondence between a texture image and control points on a manipulable character, e.g. a skeleton, was typically carried out by hand. For instance, after an image of a person is taken, a designer might label various pixels in that image as corresponding to the right wrist, left wrist, etc. and correlate them with associated control points on an animated figure. While this approach might be acceptable if a single image of a person is to be captured and labeled, it can become overly burdensome if several images are to be used as input, for example in the case where a video image of a moving child is used to control the motion of a character on the screen. Rather than hand labeling, it may be more appropriate to tag the video input of the child, for example by having him wear apparel that readily identifies the different portions of his body, e.g. green gloves, a blue hat, purple shoes, and the like. With this approach, the different colors in the input image can be used to identify the movements of the child, at least on a very gross level. The need to tag the image, however, alters its original appearance and limits the types of images that can be employed.
It is desirable therefore to provide an automated approach to the identification of jointed limbs, and the like, in a texture image, to thereby avoid the need for hand labeling of images and to permit any type of natural image to be employed, without first requiring a subject of the image to be artificially tagged, or the like.